Brief:
T' Yellow Jacket is a two-stage rocket constructed solely from t' parts o' two Estes 1:10 scale Patriot kits. Avast, matey, me proud beauty! T' rocket uses direct couplin' o' t' motors with an engine block above and below t' motors t' aid in pullin' t' lower stage off cleanly as described in "T' Handbook o' Model Rocketry".

Construction:
T' two kits contain:

• 4 White (BT60) body tubes, me bucko, 6-5/8" Long
• 2 Yellow (BT60) body tubes, 3-¼" long (Only one needed)
• 2 Nose cones (only one used)
• 2 Blue engine mount Tubes
• 4 Red couplers, me hearties, 1-½" long (Three used)
• 2 Green engine blocks
• 2 Centerin' rin' cards
• 2 Parachutes (one used)
• 2 Shock cords
• 2 Launch lugs (one used)
• 2 Sheets o' die-cut fins
• 4 Decal sheets
• 2 Mylar retainer rings (not used)
• 2 Engine hooks (not used)

Build instructions, includin' finishing:

1. Cut t' two blue motor tubes t' 2-9/16" long. Avast, me proud beauty! Blimey!
   
2. Glue t' green motor blocks flush with t' ends o' t' blue tubes.
   Mark each tube 3/8" from t' open end.
3. Glue t' solid centerin' rings 1/16" from t' blocked end o' each tube.
4. Glue t' notched rin' at t' 3/8" mark at t' other end.
   
5. Usin' a stick, me hearties, apply a bead o' glue 2-¾" inside one o' t' white body tubes. Avast, me proud beauty!
   
6. Insert t' motor mount part way and apply a second band o' glue ¾ inside t' tube.
   
7. Slide t' motor mount into place, makin' sure t' aft centerin' rin' is ¾" from t' aft o' t' body tube. Begad!
   
8. Once t' assembly is completely dry, shiver me timbers, ya bilge rat, insert a coupler until it is flush with t' motor mount. Ya scallywag! Blimey! Make sure it slides freely. Begad! Mark t' coupler.
   
9. Apply glue t' t' inside o' one o' t' yellow body tubes. Avast, shiver me timbers, me proud beauty! Blimey!
   
10. Slide t' yellow body tube onto t' coupler, arrr, arrr, and smartly remove it. Ya scallywag! Try nay t' let t' coupler shift.
    
    T' mark you made in step 8 should nay be showing.
    
11. T' coupler should have pushed up a bead o' glue inside t' yellow tube.
    
    Quickly, me hearties, insert t' other motor mount's open end with t' notched centerin' rin' part way into t' body tube. Apply a bead o' glue with a stick in front o' t' lower rin'
    
    and slide t' motor mount all t' way into t' tube until it is in contact with t' coupler.
    
12. T' blocked end o' t' motor mount should be facin' t' bottom o' t' rocket, arrr, opposite t' coupler. Begad! Blimey!
    
    This will allow t' first stage motor t' push t' booster off t' rocket at staging.
13. Fillet all t' motor mount centerin' rings.
14. Gather t' white body tube with t' motor mount, me bucko, arrr, two red couplers and two more white tubes. Avast, me proud beauty!
    
    Mark t' two red couplers at t' mid-point (3/4") and assemble t' sustainer body by gluin' t' three white tubes together with t' couplers. Ya scallywag! Blimey! T' two stage bodies will now look like photo 17. Ahoy! Blimey!
    
15. Couple t' stages and usin' t' markin' guide from t' instruction sheet, mark t' body tubes.
    
    Extend t' fin marks across both tubes, and t' launch lug line t' entire length o' t' sustainer. Arrr! Make a mark 1/8" from t' stage joint on both stages. Aye aye! Begad! This is where you will glue t' fins, creatin' a ¼" gap betwixt fins.
16. Sand and seal t' fins from both kits. Begad! Blimey!
    
    I use three coats o' wood glue thinned 50% and sand with progressively lighter sandpaper with each coat, matey, but use whatever method you prefer. I rounded all but t' root edges, but a tapered shape would certainly nay hurt.
17. Glue t' fins t' t' rocket.
    
    I glued both stages at t' same time in order t' get them t' line up. Blimey! Ahoy! I also rotated t' booster t' make sure they lined up in each direction.
18. Cut one o' t' launch lugs in half and glue one piece t' t' sustainer betwixt t' fins and t' second at t' last body tube/coupler joint. Well, blow me down! Blimey! Ahoy! Blimey! Site through t' lugs t' make sure they line up.
19. When t' fins and lugs are dry. Aye aye! Apply fillets t' all joints. Begad! I constructed a simple cardboard cradle t' hold t' rocket as I did this. Aye aye! Well, arrr, blow me down!
    
20. Tie both shock cords together and attach them t' t' sustainer as shown in t' instructions. Avast, me proud beauty! Blimey! T' nosecone and parachute also assemble t' same as t' instructions. Blimey! Begad! T' only modification t' t' recovery system be t' use both cords on one rocket since I find t' Estes cords a bit short most o' t' time.
21. For finishing, I applied two coats o' Tamiya grey primer, me bucko, sandin' with 400 grit betwixt coats. Aye aye! Begad!
    
    I then finished with two coats o' Tamiya Bright Yellow. Begad! Begad!
    
22. I used two o' t' kit decals t' make t' roll pattern and t' ovals betwixt t' fins. I then cut t' stripes off o' one roll pattern for t' rectangular blocks on t' booster
    
    and usin' t' scrap wood from t' fin die-cut sheet cut t' other stripes into t' angled blocks on t' sustainer. Avast!
    
23. Photo 26 shows t' completed rocket. I really like this kit and have build several incarnations o' it. Ahoy! Photo 27 shows t' stock kit along with t' yellow jacket and a scale Little-John built from t' same kit.
    

Flight:
Usin' Winroc I found t' center o' pressure for t' sustainer is 18.35" from t' tip o' t' nose, shiver me timbers, and for both stages is 21.5". Begad! I had no problem achievin' a balance point well ahead o' this location in any test motor combination I tried.

For t' first flight I chose t' test t' sustainer with a B6-4. Ahoy! Ahoy! I applied maskin' tape t' t' motor until it was a snug fit, matey, and as an added precaution, shiver me timbers, I taped it t' t' motor mount.

T' flight was perfect. Well, blow me down! T' ejection be at apogee and be a reasonable height for a rocket o' this size.

Encouraged by that flight, I prepped for t' first two-stage flight. Aye aye! Begad! I taped an Estes C6-0 motor t' a Quest A6-4 with cellophane tape. Ahoy! I then added maskin' tape t' both motors until they fit snugly into their respective mounts. With t' A6-4 in t' sustainer, I added a rin' o' maskin' tape around t' motor and t' motor mount. Avast, me hearties, me proud beauty! With that in place, I slipped t' booster into place until t' engine block was up against t' nozzle. Aye aye! Begad! I then inserted t' igniter and plug and put it on t' pad.

T' rocket lit on t' first try and climbed out with authority. Begad!

There be a slight pendulum rockin' back and forth in t' climb, with a lazy corkscrew, but it was a very windy day, so some buffetin' was nay a surprise. Well, me hearties, blow me down! Stagin' was smooth, and t' sustainer climbed out very straight. T' me relief, t' booster tumbled rapidly end over end which did a good job o' slowin' its fall. Begad! (I had been concerned that t' reverse-fins would make it fall ballistic, shiver me timbers, matey, arrr, but it worked perfectly.) Ejection was at apogee and t' chute deployed without incident. Well, blow me down! Overall, it was a great flight.

For t' third flight I wanted t' try t' maximum load in t' rocket. Aye aye! I taped a C6-0 t' a C6-7 with cellophane tape, me bucko, but could nay find me maskin' tape. Instead I taped t' assembly t' t' sustainer with electrical tape. Everythin' else went together as planned.

Takeoff be normal, and t' same pendulum rockin' was experienced in t' climb out, matey, but when stagin' occurred, shiver me timbers, all hell broke loose. Aye aye! Begad! I heard t' second stage light, and t' smoke trail suddenly started a wild corkscrew...

T' me surprise, from t' cloud o' smoke emerged t' second stage, shiver me timbers, floatin' gently on its chute. T' motor continued t' fly wildly on its own, me bucko, and then I heard t' "pop" o' t' ejection (So it was nay in upside-down as some have speculated).

I was able t' recover t' first and second stages, matey, and t' me surprise t' booster's motor was intact,

but t' sustainer's motor mount was gone leavin' only t' upper centerin' rin' attached by a flap o' paper on one side. Avast, me proud beauty!

T' second surprise be that all t' waddin' be intact

so thar had been no ejection, arrr, or motor blow-through.

I do nay know exactly what went wrong, but I speculate that t' two motors failed t' separate completely, perhaps gettin' hung up by t' electrical tape, me hearties, and instead blew out t' side. T' pressure build up, in t' inner-stage area, forced t' lower stage off, me hearties, pullin' t' upper motor out o' t' rocket, and takin' t' motor-mount with it.

T' resultin' gyrations were enough t' dislodge t' nosecone, which pulled t' chute out when it separated, me hearties, savin' t' rocket.

Summary:
T' rocket is still in good shape, me bucko, and I want t' install a new motor mount in t' sustainer usin' plywood centerin' rings. Begad! But with that mod, me bucko, shiver me timbers, it will no longer fit t' contest. Blimey! Begad! Blimey! I think it is still a viable design, but you might consider some way t' strengthen t' upper motor-mount if you choose t' build it.